Conventionally, as an airflow volume sensor installed in an intake air passage of an internal combustion engine of a car or the like to measure an intake air volume, a thermal type sensor is becoming mainstream since the thermal type sensor can detect a mass airflow volume directly.
Recently, an airflow volume sensor in which a film of a resistor and an insulating layer is deposited on a silicon substrate by means of a semiconductor micromachining technique, part of the silicon substrate is thereafter removed by a solvent represented by KOH or the like, and a thin film portion (a diaphragm) is formed attracts attention since the airflow volume sensor has quick responsiveness and can detect backflow, taking advantage of the quick responsiveness. Also, in recent years, for the purpose of reducing the number of parts of a substrate portion (a printed substrate, a ceramic substrate, or the like), the airflow volume sensor of a transfer mold package type is being considered, in which the airflow volume sensor is implemented on a lead frame, and in which an outer circumferential portion thereof is molded by a plastic.
In a case in which a semiconductor circuit element such as an LSI and a microcomputer is molded, the circuit element and the lead frame are bonded with use of an adhesive sheet in many cases. In a general method for using the adhesive sheet, the adhesive sheet is stuck to a back surface side in a state of a semiconductor circuit wafer, and by cutting the adhesive sheet layer simultaneously at the time of dicing the wafer in a dicing process, the adhesive sheet is in a state of being stuck to an entire back surface of each semiconductor circuit chip. It is advantageous in that a process of printing a solvent as in a case of using a solvent-type adhesive can be omitted since the diced semiconductor circuit element can be implemented on the lead frame as it is.